Londoll in U.S. Pat. Nos. 4,228,277 and 4,243,802 describes how to make and use a new viscosimetric material, i.e., hydrophobically modified cellulosic ethers. Some self associating hydrophobically modified hydroxyethylcellulases are now commercially available from Aqualon Company, a Hercules Incorporated Company, and these have found wide acceptance in coatings applications. Other self associative hydrophobically modified cellulose ethers are involved in experimental and developmental work.
Interactions of hydrophobically grafted cellulose ethers were described in the publication, "Hydrophobic Microphase Formation in Surfactant Solutions Containing an Amphiphilic Graft Copolymer," Dualeh and Steiner, Macromolecules, 1990, 23, 251. Association between water-insoluble C.sub.12 -grafted hydroxyethycellulose and sodium dodecylsulfate gave rise to viscoelastic solutions and hydrogels with dispersed hydrophobic microdomains. It was speculated that applications could be uncovered for these hydrogel phases.
Yet In spite of what was known concerning the utility of hydrophobically modified cellulose ethers, the full sccoe of their employment was not obvious to different artisans for different applications. Thus it remained for the present invention to expand the state of the art for the new class of materials which had come to be known as associative thickeners.